Commercial and industrial liquids of all types are stored in underground and above ground storage tanks. The capacity of such tanks are at least 500 gallons liquid and typically are 10,000 to 50,000 gallons liquid. The tanks presently being sold are made of metal or a fibrous reinforced resinous material. The metal storage tanks are made of a heavy gauge steel and are cylindrical-shaped. They are normally wrapped or coated with a non-corrosive material. The fibrous reinforced resinous material underground storage tanks are usually ribbed for added strength. The above ground tanks which are generally vertically disposed do not have ribs. However, they are most preferably filament wound for strengthening purposes.
Regardless of the material used to make the underground storage tanks, the tanks must have sufficient wall strength to withstand internal and external weight forces. Increased wall thickness does increase wall strength, but also increases the cost of producing the tank and the added weight increases the cost of installing it. Clearly, any leakage from the tanks, whether due to a complete collapse, a rupture, a crack or a small hole can have a substantial impact on the environment or health of nearby residents.
A need for an underground storage tank which can safely hold a substantial amount of potentially dangerous liquid is well recognized. Double walled storage tanks have been suggested. Various new methods of building tanks have also been suggested in recently issued patents. Still more efficient and cost effective methods of making reliable storage tanks are needed. In accord with this continuing need, there has been developed a double wall storage tank system with walls bonded together and with leak detection capability. The tank systems are economically built and are installed with conventionally used equipment.